Step 1: Boil 4 cups of filtered water in a large pot. Remove from heat and add the black tea bags (or loose-leaf tea) and granulated sugar. Stir until the sugar is completely dissolved.
Step 2: Let the tea steep for 10-15 minutes, then remove the tea bags or strain out the loose-leaf tea. Allow the sweet tea to cool completely to room temperature. This is a critical step; hot tea will kill your SCOBY.
Step 3: Pour the cooled sweet tea into a clean, 1-gallon glass jar. Add the remaining 8 cups of cold filtered water to the jar.
Step 4: Gently place your SCOBY into the tea. Add the 2 cups of unflavored starter tea. This liquid is essential for lowering the pH and preventing mold.
Step 5: Cover the mouth of the jar with a breathable cloth (like a coffee filter or cheesecloth) and secure it with a rubber band. This allows air circulation while keeping out contaminants.
Step 6: Place the jar in a quiet spot away from direct sunlight, at room temperature (ideally 68-78°F / 20-26°C). Allow to ferment for 7-14 days. Begin tasting after 7 days; it should be tart and slightly sweet. Ferment longer for a more vinegary taste. Look for a new SCOBY forming on the surface as a sign of healthy fermentation.
Step 7: Once your F1 kombucha has reached your desired tartness, carefully remove the SCOBY and 2 cups of the finished kombucha. Store the SCOBY and starter tea in a separate container for your next batch.
Step 8: Prepare your chosen flavorings (e.g., chopped fruit, fruit juice, ginger) and divide them among clean, airtight glass bottles, leaving about 1 inch of headspace.
Step 9: Pour the fermented kombucha from F1 into the prepared bottles and seal tightly.
Step 10: Place the sealed bottles at room temperature for 2-5 days for the second fermentation (F2). This is where carbonation builds. 'Burp' your bottles daily by carefully opening and resealing them to release excess pressure. Once desired fizziness and flavor are achieved, transfer bottles to the refrigerator to slow fermentation and carbonation. Enjoy chilled!